What are the criteria of worthy kill for you? And what criteria are for unworthy?

We've got some skill here. We've got help file for that skill. We've got a tablet inside of the village and kinda history of the Battleragers in the Lyceum. I read them all and I didn't found any hint for "proper" using of the trophy skill except of poor whining here in comments. So elaborate your point for what reason you would uninduct somebody who's using this skill? Otherwise I would suggest you uninduct your.. cat or whatever pet you've got.

Marla was supposed to have terrible, unpleasant, rude and arrogant character, she was drow (which is evil, right?) and probably would skin you even alive if only this would be possible. I'm not talking about my poor RP realization (unfortunately), but still.